This invention relates to a cable connection for a rotational assembly designed to permit a limited number of rotational turns, and, more particularly, to the structure promoting efficient cable takeup and payout.
Many industrial designs utilize structures wherein one component rotates relative to another, and wherein the rotating component requires a power, instrumentation, optical fiber, fluid, or other type of hookup connection to the non-rotating component. Some such structures require an infinite relative rotational capability. In these cases a hookup connection can be made using sliding contacts or rotational connectors.
Other structures require only the capability of some finite number of relative rotations, which is herein termed a "multi-rotation assembly". In the case of a multi-rotation assembly, power, instrumentation, fluid, or other hookup connection between the rotating and non-rotating components can be conveniently made with a cable that is wound and unwound during the rotational movement. A cable has the advantage over sliding contacts or rotational connectors of reduced chances of failure due to bad contacts or connector failure, less noise in the case of an electrical connection, and less likelihood of leakage in the case of a fluid rotational coupler. The present invention is concerned with such a multi-rotation assembly.
In providing cable hookup connections in multi-rotation assemblies, it is well known to provide a central hub that is rotatable within a hollow housing. A cable is connected at one end to the hub and at the other end to the housing, and is circumferentially wrapped in the space between the outside surface of the hub and the inside surface of the housing. The cable is payed out as the hub is rotated in one rotational direction (e.g., clockwise rotation) and taken up as the hub is rotated back in the other rotational direction (e.g., counterclockwise rotation). Care is taken to avoid twisting or kinking of the cable, and to ensure a smooth, repeatable unwinding and winding of the cable. The length of the cable corresponds to the length required to supply the number of rotations for which the hub is designed. A number of designs have been developed to accomplish these objectives.
While operable in many situations, the available approaches have some shortcomings. The space between the hub and the housing limits the amount of cable that can be wound. Consequently, the number of rotations permitted for the hub is often limited by the permitted length of cable, particularly where the cable is of relatively large diameter such as a Dower cable or hydraulic cable. Existing designs therefore limit the number of available rotational turns to less than that needed for some applications. The cable may itself be expensive, and the present deigns require more cable than is desirable.
There is a need for an improved takeup/payout system for cables in multi-rotational systems. The present invention fulfills this need, and further provides related advantages.